I just changed the (dead) Meoldy ignition for a new Rxcel igniton on my SPE 40 - the new ignition came with its own hall sensor , but I have no spark - and I see the air gap between the magnet and the sensor housing is 2.25 mm - is that too great to generate a spark ?
What should the max air gap be ?
Thanks
Grant

i think it is too big gap
should be 0.8 to 1mm, as the HAL sensor is a "wire-coil) that change its own elctromagnteic field each time the magnet cross the field, so if the gap is too big, the elctro-mag field remains the same-> no signal to the IGI unit-> no spark!

can u please post some pics so we can get a better look on the matter?

I could post a pictue, but it doesnt tell you anything more than I have said - when the hall sensor has been put in place , it sits over 2mm above the magnet that passes under it, so I need to find a way to lower the hall sensor

The wrong side of the magnet could be facing the hall sensor. Hold the sensor upside-down and flick the magnet past it to see if you can get a spark.

Yup what Maddog said. Could be the gap though. I had the same problem on a SPE 26 I bught a couple years back that had been converted by the dealer to Rcexl. The gap was such that it would start, but then would die after 20 to 30 seconds. It would not restart until it cooled down. Turned out the gap was just at the point it would fire and as soon as it started to warm up the gap would increase just enough to make it stop. Took quite a while to figure it out and solve. Once I reduced the gap it ran properly.

Aim for a gap of 0.5 to 0.7mm
Any larger may get you in trouble.

@ Gadi
RCexcl ignitions do not use a coil, but switch conductance when near the right magnetic polarity.

The hall sensor is not bi-polar, so it is sensitive to the magnet polarity. The RCexcl manual included with the ignition shows how to test and fit the sensor so the ignition will work. Only when working OK, should the sensor be secured in the housing with the small taper thingy that is included.

The magnet is the one that is fixed in/ on the shaft of the engine , in a bored hole. its the sensor that has been replaced as its the one that came with the new ignition. I still have the original sensor , which obviously fits at the correct airgap - but I dont know which wires would equate to the Rxcel ignition - the Melody pickup has a proprietry white three pin connector, the Rxcel has a std Futaba type plug ( why dont these mfrs standardise on these things ...)
They are both three wire though , but not the same colours ....so if anyone knows which wire goes where , from Melody to Rxcel I could fit the Melody sensor to try it . I doubt it would blow anything up ?

I cant raise the magnet, as its fixed flush in the shaft, but the sensor is screwed to a clamp that fits over the motor housing ....so its possibly the only way to solve this ...to lower it

PS - I didnt receive any manual with the ignition....and no magnet was supplied -if there was a special magent , surely it should have been supplied ?

I just found the manual on line and see what you mean about the north / south orientation of the hall sensor - I now assume its been inserted upside down so will take it out and test it ..that may be the answer . Shame , there were no instructions , I will advise the supplier , as this is most important.

Most likely that is the problem (upside down) as you have no spark at all. I lowered my sensor on the 26 by reshaping the holder so the tip of it was angled down closer to the magnet. I am not sure if the hall sensor from the melody ignition would work. Best to stay with the Rcexl sensor.

just tested it - it was upside down, and I now have spark - but refitting the sensor the stock mount system still leaves no spark as the air gap is too big ...so I know it works, but have to now get the air gap down ....not a simple one at first look ...but I at least have sloved the problem ...there were two problems.

Most ignitions do not come with a magnet, so a lack of instructions in that regard would not be abnormal. Most ignitions arrive with a new engine, and replacement ignitions rarely involve replacing a hall sensor, with replacing the magnet an almost unheard of event. Even when replacing hall sensors alone magnets are not involved.

This is a case where a picture or three might be a good thing since we don't know the hub relationship to the case and hall sensor bracket.

Instead of reshaping your Rcexl holder you may be able to insert the Rcexl hall sensor into the Melody holder. Be sure to check the timing after as well. I had to extend the groves in my holder to move it enough to set the timing.

Not possible - the Melody sensor is a moulded unit ....what I might do is take the sensor out of its housing and glue it underneath with silicon , then make sure it works ...then epoxy it for security
underneath the housing will bring it much closer to the magnet